Some of seat belts mounted in automobiles use a connector belt which holds both one shoulder and the loins of a passenger. Many of these seat belts have a slip anchor passing through the central portion of the seat belt to hold the central portion and correctly fasten one shoulder of a passenger in conformity with the sitting height and the physical make of the passenger. The anchor is mounted to a stationary portion of the automobile body, such as a center pillar, so as to be vertically adjustable.
In the conventional seat belt-anchoring device of this kind, a slide anchor is movably mounted to a rail member extending vertically. The rail member is rigidly fixed to a stationary portion of the automobile body, such as a center pillar. An anchor bolt is firmly attached to the underside of the slide anchor. The slip anchor which passes through the seat belt and guides it is rotatably held by the anchor bolt. A retaining pin that is always urged to protrude by a leaf spring is mounted over the slide anchor so as to be capable of protruding rearward from the back surface of the slide anchor. A knob that can be operated by a person is formed integrally with the pin. Some holes are formed in the rail member longitudinally, and the front end of the pin can be inserted into any one of these holes so as to be withdrawable. If necessary, the knob is pulled to withdraw the pin integral with it from one hole in the rail member. Then, the slide anchor is free to move vertically. In this state, its height can be easily adjusted.
In the conventional seat belt-anchoring device constructed as described above, it is necessary to allow the slide anchor to move a long distance, for preventing the knob on the pin from interfering with the slip anchor. This narrows the range in which the height can be adjusted. Further, the weight of the assembly increases.
If the whole length of the rail member is increased, then the range in which the height of the slide anchor can be adjusted is enlarged. However, the upper and lower points at which the rail member is fixed are spaced more widely and so the central portion bends easily. Elongating the rail member increases the weight and the space needed for installation accordingly.
Also in the prior art seat belt-anchoring device, the retaining pin is required to be pulled against the action of a biasing spring to withdraw the pin from one hole in the rail member. Then, the slide anchor is moved vertically. Therefore, the device is difficult to operate with one hand.